Funny. I am running the latest Flash Player on Windows XP, Windows Vista, Windows 7, Windows 8, OS X 10.7.5, OS X 10.8.4, Linux Mint 15, Linux SuSE 12, Linux Ubuntu 13, and Linux Fedora 17. I'm pretty sure if it was the Flash Player that was incompatible with anything and everything everywhere, I'd have at least one problem in ten different Operating systems, which I don't.
You can find older versions here: http://helpx.adobe.com/flash-player/kb/archived-flash-player-versions.html
Thank you ever so much with your helpful insight, it was a pleasure to read your helpful detailing of how to sort out the problem... or, you could try not being a 'I've got nothing to do here that reeeally helps but I feel like a big head so I'm going to post anyway' internet geek when there are people who have been suffering from this issue for ages...
That is just a smattering of the issue, I'm not going to keep on posting links just for the hell of it, just search 'stuttering video audio in flash', have a nice/great/wonderful/awesome day.
Suffering? "Oh, the humanity! We need legislation to end this RIGHT NOW!!!!!"
Here's what you NEED to do:
1. Go though ALL of your browser plugins to see which, if any cause conflicts with Flash websites. Disable them.
2. Clear your browser cache.
3. Run a thorough disk cleanup to get rid of old junk files that are slowing your system down.
4. Run a defregmentation of your hard disk to make sure that it isn't bogging your system down.
5. Go through ALL of your installed software, to make sure you don't have anything that might be causing performance issues and/or conflicts with Flash Player. (other video players for example)
6. Update your network adapter, sound card and display adapter drivers.
If, after all that, it still doesn't work properly, I provided a link where you can download an older version that IS compatible with your system configuration. That's where the problem lies, in your configuration.
There are literally BILLIONS of computers around the world on which Flash Player DOES work properly so don't treat this like it's a "universal problem" and you're just complaint number 14,889,675, 382,543 of fifteen trillion, and it's ALL Adobe's (or my) problem to fix, when it clearly ISN'T broken or NOBODY'S would work.
Grow up and take some responsibility for your own stuff.
I've been trying to fix this for ages on two machines, I've done all but maybe the first of your recommendations, even then the first I've most likely done and as I've found no conflict then it comes down to the machine vs flash. It's flash btw. Adobe have admitted as much in previous comments so hey... I'm going to rant, you came along not knowing what is going on and walked right into it with... no... I'm going to offer an apology instead. Sorry for ranting at you, this is just driving me crazy is all.
I'm happy your machines are bug free in this case, I'm glad your not experiencing this problem as there isn't an easy fix as such, even after following other mini tutorials closely I still update to 11.7, I'm also glad that your obviously willing after 3300 odd posts to attempt to help.
I however am not alone, this is an issue raised more than once or twice over various platforms and over loads of forums, taking into account the times it hasn't been reported properly and people have said look to your Dx, your drivers your blah blah blah when it Is Adobe's 11.3+ build, the one that Adobe have failed to fix after various new releases so obviously deem it too small a population of machines to bother with it, yet for people like myself who are able to use some advanced functions on a pc yet can't seem to fix this one simple damn thing it becomes first a nuceance, then an issue to then right out a frikkin pain, all because everything within the software of these programs are designed to update by default. So for me it is an annoying thing, above annoying as I want to use youtube for both home and work.
So yes, the main issue is Adobe's build, they said so themselves and have identified the cause when they changed... something, I can't remember but again, on the first link it leads to it I think... It doesn't always work on some builds and that is the case here anyway. As for the old 10.x version taking on my pc I'm stumped. As for it being your problem, no, it isn't, you are however here to help (or gloat, your choice here on either), not take comments aimed at Adobe personally Or explain how wonderful your machines are working, again, good for you. It doesn't help the issue though okay. That just pours salt into a wound.